Method for packing items or loose material in suspended film bags.
The present invention relates to a method and an apparatus for packing items in film bags which are conveyed through a filling station in a continuous web where a filling of the individual bag items is performed, which bags are then closed and separated from the continuous web for establishment of individual packings.
A basic example of this technology is mentioned in EP-696997 in which it is stated that the opposite upper edge areas of the bag item web is made with bent rim parts formed by grooves for drawing in on conveyance bars which have a mutual expansion for producing an opening of the bag items in the direction of conveyance, such that these can be filled, for example through a superjacent funnel, where after the conveyance bars are narrowed against each other again for temporary closing of the filled bag items. These can then be closed completely by welding below said groove parts where after these are cut off and the items mutually separated. As an alternative it is stated that instead of groove parts, edge thickenings may be applied which may be received in slotted conveyance pipes for a quite corresponding conveyance of the bag items.
Since then other types of means have been suggested for catching and carrying the opposite upper edges of the bag item web, for example as stated in EP 0 555 321 B where special catching chains are used for the purpose without special requirements to the design of the upper edge areas of the folded bag item web. This is of substantial significance in that as an end product a simple rolled op flat film web without local thicknesses may be used, however in return there are considerable problems with regard to both the guidance of the opposite edges of the bag items for a safe engagement with the chains and with regard to a desirably inexpensive embodiment of these chains.
In EP 0 396 838 and EP 0 825 116 it is furthermore stated that a flat pipe web of the film can be applied which can continuously be cut open along its upper edge with integrated unfolding and catching of the thus cut open upper edges without these being specifically designed neither as grooves nor with thickenings which will indicate a distinct simplification of the requirements for the production of the bag web. The cut open upper edge parts are unfolded to be squeezed between respective moving belts made with longitudinal recesses and corresponding pressing cords whereby a suitably firm carrier engagement can be established.
However, this engagement is not firmer than axial slidings may occur between the upper edges of the bag web and the associated means for belt transport whereby uncertainty may arise as to whether a conveyed item has been conveyed completely synchronously with the conveyor belts. Moreover, deviations may arise with regard to height location of the area of the web sides that is squeezed between the conveyor belts which may be of importance as to whether the filled bags are completely closed at the location intended for this exact purpose, for example in relation to print on the bag.
In DK PA 1998 00548 is described a construction which uses a simplified flat bag web as said opening edge is merely closed when the web is introduced on a single carrier bar and is continuously cut open in a station where the thereby upright rim strip parts are unfolded in order to be laid down on opposite chains. In advance, these strip parts are made with a row of holes which are led down into upwards directed holding studs on the carrier chains during folding down whereby a safe carrier and propelling engagement is achieved without any special profiling of the opening edges.